Lesson 7: Types of Synchronization Flashcards
Means that the receiver must be able to determine when to expect a new transmission and when to send acknowledgements.
Synchronization
In the context of .NET, is a process that involves coordinating the execution of multiple threads to ensure a desired outcome without corrupting the shared data and preventing any occurrence of deadlocks and race conditions.
Synchronization
It usually uses a clock signal transmitted in sequence with a data stream to maintain proper signal timing.
Synchronization
Occurs between network nodes to ensure that data streams are received and transmitted correctly, and to prevent data collision.
Synchronization
is to coordinate or time events so they happen all at the same time
synchronize
To cause objects or events to move together or occur at the same time
synchronize
refers to the method used by the data communication system so that the destination station recognizes the start of a data stream and reliably reads the information sent.
Timing
Two major timing schemes are used:
- Asynchronous Transmission
- Synchronous Transmission
sends data from the source to the destination without synchronizing the two clock systems.
Asynchronous communications or transmission
used for low data transfer rates usually 128 kbps or less and short bursts of data.
Asynchronous communications
Conventional representation has asynchronous data flowing
left to right
Conventional representation has synchronous data flowing
right to left
indicate the end of data
stop bits
The characters are sent individually with a quiet period in between (quiet meaning 0 bit level).
Asynchronous transmission
means that the clocks are not locked together
Free running
Is a method of data communication that requires the source and destination to synchronize their clocks together.
Synchronous transmission
Two types of synchronous data transmission (or communication):
- Externally clocked synchronous transmission
- Internally encoded synchronous transmission
This synchronization of the clocks can occur externally to the data information or be incorporated with the data information.
Synchronous transmission
With synchronous transmission, blocks of data up to ___ in size can be sent without loss or corruption of data.
64Kbytes
is required for the amount of data sent.
Less overhead
In asynchronous transmission, there are ___ of overhead (start, stop, parity bits) sent with each character of data (7 to 8 bits).
3 to 4 bits ;
Indicate the beginning and end of transmission.
start field and end field
results in a more efficient delivery of data
Smaller overhead
has separate lines from the data lines for synchronizing the clock.
Externally clocked synchronous transmission
is used to send out a timing clock to the destination
Transmit Timing balanced pair
is a separate clock timing received from the destination.
Receive Timing balanced pair
Special sequence of bits called _____ are required at the beginning and end of the block of data to inform the destination that new data is arriving.
fields
sends blocks of characters at a time.
Synchronous Transmission
Each block of data is preceded by a ____ which is used to tell the receiving station that a new packet of characters is arriving.
Start Field
Indicates the end of the data block
End Fields
The packet can contain up to ___ depending on the protocol.
64,000 bytes
Synchronous transmission is more efficient than asynchronous (character transmission) as little as only ___ are required to transmit up to 8K bytes
4 bytes (2 Start Framing Bytes and 2 Stop Framing bytes)
Extra bytes, like the Start and Stop Frame, that are not part of the data are called
overhead
Consists of control information used to control the communication.
Overhead
Efficiency formula
Efficiency = # of data bytes / total num of bytes transmitted
An Ethernet frame has an overhead of 26 bytes including the “Start and Stop Frames”, the maximum data size is 1500 bytes.
The Ethernet frame’s efficiency would be ___ efficient.
98.3%
Is more difficult and expensive to implement than externally clocked synchronous transmission.
Internally clocked synchronous transmission
is an example of an internally clocked synchronous transmission code.
Manchester encoding
The timing signal for synchronization between the source and destination is encoded within the data stream.
Internally clocked synchronous transmission
Internally clocked synchronous transmission is often called____ as no external timing lines are required.
self clocking
In the Manchester Code, there is a transition at the ___of each bit period.
middle
Has no DC component and there is always a transition available for synchronizing receive and transmit clocks.
Manchester Encoding
Manchester Encoding is also called a ___
self clocking code
Manchester Encoding requires a
Narrow Bandwidth
The ____ is used as an introduction to Synchronous Data Transmission.
Generic Packet X
At the beginning of each frame (packet), there will be a sequence of bytes (8 bit words), called the
Preamble
The ___ is a series of bytes with a specific bit pattern that is used only by the Preamble.
Preamble
The Preamble is used to:
Inform the receiving station that a new packet is arriving
Synchronize the receive clock with the transmitted clock
Names used by other protocols for the Preamble are:
Starting Delimiter, Alert Burst and Start of Header.
Starting Delimiter/Alert Burst/Start of Header
Preamble
Source and/or Destination
Address Field
The Source and Destination Addresses are ____ numbers that identify the sender Source and receiver Destination.
hexadecimal
reside in either the Network Interface Card’s firmware or can be either assigned during the initialization of the NIC.
Network Addresses
The purpose of the ____ is to identify to the network who is sending data.
Source Address
The purpose of the ___ is to identify to the network who should be receiving the data.
Destination Address
is used to indicate the
Type of Information being sent as Data.
Control Field
The purpose of the ___ is to identify what the purpose of the packet or frame is: Control or Data. It can also be used to indicate the size of the packet and Data.
Control Field
Is the actual information that is being transmitted
Data Field or Message
It can contain Control Information for handshaking or actual Data used by applications.
Data Field or Message
The Data field is also called the ___ by some protocols
Info field
The Control Field would indicate the ____
Data Field size
is used to pad the data field when the protocol has a fixed Data Field size.
Optional pad
If the Data Field size is fixed at 1200 bytes and only 300 bytes of information is available then the Pad will fill in the remaining ___ with characters
900 bytes. (e.g. 900 bytes of 00h)
contains an error checking number that the Destination can use to verify that the packet is okay and error free.
CRC / Frame Check Sequence (FCS)
FCS
Frame Check Sequence
CRC
Cyclic Redundancy Checking.
The Frame Check Sequence typically incorporates a ___ check.
32 Bit CRC
As each packet is sent, the ___ calculates a check number from the data using a predetermined algorithm (formula).
Source
The result of this calculation is appended to the packet in the ____
Frame Check Sequence (FCS) field.
At the _____ , the same calculation is performed and the result is compared to the transmitted Frame Check Sequence.
Destination
If the result generated at the Destination is identical to the FCS, then it is assumed that
the packet is error free at the bit level.
is a series of bytes that have a specific bit pattern that identifies the end of the packet to the Destination
End Frame Delimiter
is simple and inexpensive to implement. It is used mainly with Serial Ports and dialup connections.
Asynchronous transmission
Requires start and stop bits for each character this adds a high overhead to transmission
Asynchronous transmission
is more efficient as little as only 4 bytes (3 Start Framing bytes and 1 Stop Framing byte) are required to transmit up to 64 kbits .
Synchronous transmission
is more difficult and expensive to implement
Synchronous transmission
It is used with all higher communication transfer rates: Ethernet, Token Ring etc…
Synchronous transmission
is used in fast transfer rates typically 56 kbps to 100 Mbps.
Synchronous
Advantages of Asynchronous
Simple & Inexpensive
Disadvantages of Asynchronous
High Overhead
Advantages of Synchronous
Efficient
Disadvantages of Synchronous
Complex and Expensive
Types of Synchronization
- Data synchronization
- Process synchronization
Involves the maintenance of data to keep multiple copies of data coherent with each other, or to maintain data integrity.
Data synchronization
The simultaneous execution of multiple threads or processes to reach a handshake such that they commit a certain sequence of actions.
Process synchronization
is an abstraction that allows at most one thread to own it at a time
Lock
____ is typically an integer variable whereas, ____ is an object.
Semaphore; mutex
allows multiple program threads to access the finite instance of resources
Semaphore
allows multiple program threads to access a single shared resource but one at a time.
Mutex